There has conventionally been known an electronic control unit in which a current circuit part including a switching element, a control circuit part which controls actuation of the switching element to control a control target, and a current input part to which a current flowing in the control target is input via the current circuit part are provided on one substrate. For example, the electronic control unit described in Patent Literature 1 is used to control a motor of an electric power steering device. During the control of the motor, a large current flows in the current input part and in the current circuit part.